Science side here: The flash coming off of the lightning is very fast. Your phonecamera’s shutter actually takes the photo from side to side. The flash of lightning (or perhaps another lightning) struck while it was in the middle of photographing, leaving half of the photo being from before the flash, and the other half during it.

Science Fiction side here: What really happened was a tear in the fabric of reality. During that fraction of second you camera was able to pierce through the veil that separate this dimension from the mirror-image one, also known as mirror universe. Your alternate self probably did the same, at the same time. You alternate self also has a goatee and/or an eyepatch.